-ous

from The Century Dictionary.

• A suffix of Latin origin, forming, from nouns, adjectives denoting fullness or abundance, or sometimes merely the presence, of the thing or quality expressed by the noun, as in callous, famous, generous, odious, religious, sumptuous, vicious, etc. (see etymology).
• noun In chem., a suffix used to denote the presence in a compound of a relatively electronegative constituent in smaller proportion than in the corresponding compound of which the name bears the suffix -ic. In each case the suffix is attached to the name of the relatively electropositive constituent, as ferrous oxid (FeO) and ferric oxid (Fe₂O₃), stannous chlorid (SnCl₂) and stannic chlorid (SnCl₄).

from the GNU version of the Collaborative International Dictionary of English.

• suffix An adjective suffix meaning full of, abounding in, having, possessing the qualities of, like; as in gracious, abounding in grace; arduous, full of ardor; bulbous, having bulbs, bulblike; riotous, poisonous, piteous, joyous, etc.
• suffix (Chem.) A suffix denoting that the element indicated by the name bearing it, has a valence lower than that denoted by the termination -ic

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• suffix Used to form adjectives from nouns.
• suffix chemistry Used in chemical nomenclature to name chemical compounds in which a specified chemical element has a lower oxidation number than in the equivalent compound whose name ends in the suffix -ic. For example sulphuric acid (H2SO4) has more oxygen atoms per molecule than sulphurous acid (H2SO3). See Inorganic nomenclature.